Yeah the idea/process had to come from somewhere. Would be interesting if the red lyrium tattoos on those elves...
But wouldn't it not only infect the elves with the blight (which we can hand-wave because ancient elves, maybe), but start infecting the world? We don't see that until they start mining it specifically. So maybe it's
I don't know.
Not sure! We don't really know if they are red lyrium tattoos, that part is just speculation. We do know the coloration of their vallaslin is red. I don't think ancient elves are immune to lyrium corruption though. We have a likely case with Andruil, and then a definite case with Solas in the alternate version of Redcliffe. Also those paintings that seem to perhaps suggest red lyrium.
One theory- if the blight comes from the void, and the void is the domain of the Forgotten Ones, perhaps their thralls have an immunity?
If there is a mind behind the blight, and that mind has something to do with the Forgotten Ones, that would also explain why Fen'Harel was able to transverse the void without corruption. [Where as Andruil could not.] They considered him to be on their side before he betrayed them.